1. Field of the Invention
The present invention relates, in general to a method of preparing N-alkylated aminoalkylphosphonates and particularly concerns an improved process for preparing such compounds with a low acid number.
2. The Prior Art
N-Alkylated aminoalkylphosphonates are well known and can be prepared by various techniques. Examples of these techniques are found in U.S. Pats. No. 3,268,450 and 3,555,124. These patents generally disclose the process: ##STR2## The water formed as a byproduct of this reaction is removed during the course of said reaction.
Other similar techniques wherein water is not removed until completion of the reaction are disclosed in U.S. Pat. Nos. 2,635,112; 2,847,442; 2,870,190; 3,076,010; 3,257,479; 3,314,957; 3,821,335 and 3,855,363.
Additionally, techniques wherein nonaqueous aldehyde or ketone is used in a similar reaction are disclosed in U.S. Pat. Nos.3,134,742; 3,257,479; 3,352,948; 3,385,914; 3,457,333; 3,498,969; 3,505,431 and 3,551,422. Products having a low acid number can be obtained by these techniques wherein nonaqueous aldehyde or ketone is used.
The present invention constititutes a significant improvement over the foregoing prior art. According to this invention, N-alkylated aminoalkylphosphonates having a low acid number can be made by utilizing aqueous aldehyde or ketone and by following the particular reaction procedure set forth in the present specification. It is desirable to obtain a low acid number product as this eliminates the need for a final and expensive distillation step. The procedure described has the advantage that nonaqueous aldehyde or ketone, which is undesirable to handle, does not have to be handled pursuant to the present invention.